Add a value range analysis phase to remove bounds checks.

lib/compiler/implementation/ssa/types.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 abstract class HType {
   const HType();
 
   /**
    * Returns an [HType] that represents [type] and all types that have
    * [type] as supertype.
@@ skipping 124 matching lines @@
   const HUnknownType() : super("unknown");
   bool canBePrimitive() => true;
   bool canBeNull() => true;
 
   HType union(HType other) => this;
   HType intersection(HType other) => other;
 }
 
 class HConflictingType extends HAnalysisType {
   const HConflictingType() : super("conflicting");
-  bool canBePrimitive() => false;
-  bool canBeNull() => false;
+  bool canBePrimitive() => true;
+  bool canBeNull() => true;
 
   HType union(HType other) => other;
   HType intersection(HType other) => this;
 }
 
 abstract class HPrimitiveType extends HType {
   const HPrimitiveType();
   bool isPrimitive() => true;
   bool canBePrimitive() => true;
   bool isPrimitiveOrNull() => true;
@@ skipping 662 matching lines @@
   operator [](HInstruction instruction) {
     HType result = _map[instruction];
     if (result == null) return instruction.guaranteedType;
     return result;
   }
 
   operator []=(HInstruction instruction, HType value) {
     _map[instruction] = value;
   }
 }